under exposure when shooting strobe on wider angle?

Hello:

I’ve just returned from three weeks in PNG fooling with my new camera.

I have mastered the techniques used in close up work quite well, although improvement is always needed.

However, my wide angle work is absolutely terrible! Without the strobe shooting natural light - no worries. But as soon as I introduce the strobe a have hassles. I was not overly worried as I concentrated on my macro work for three weeks.

I am shooting manual (1/60th shutter speed) with an aperture of F 5.6 and adjusting for exposure using the intensity produced by the strobe power settings. ISO was 50. All my images are very very underexposed (dark). Even when I got in close to my subject the image is underexposed. How do people counteract this? The flash was extended to full arms length and set to high. The flash head was aimed behind the apparent location of the object to take into account increased size and closeness when underwater. If you lower the shutter speed too much you will have camera movement. Any hints appreciated. Thanks…….Iain

Hi Ian.

Suggest you get all this kind of thing figured out at home, before the dive trip!

I've done the same thing, a couple of times.

Anyway, I wonder if your strobes might be going off at the wrong time. Maybe they are going off on the pre-flash, and dumping all their power then, with nothing left for the real flash. Maybe your strobe or slave or whatever has a switch for this..??

I'd hook it all up on land, and start playing with it, with the srobes in close, firing right at something in front of the lens, so there can be no doubt about their power. Then start experimenting, and look at the results in camera, with histogram on.

Good luck.

Don

Thanks Don. My camera set up only arrived the day before I left for PNG - but what you say is very good advice!

Pre flash could be it, although I don't think so as my macro work is perfectly exposed. The light from the flash just does not seem to make the distance for some reason. Good idea about taking soeme pictures on land with it. I'll take your advice here - cheers. Take care...........Iain

Iain,

Things that effect the exposure of strobe lit foreground are ISO, F Stop, Number of Strobes, Strobe Aiming and Strobe power. Speed has no effect.

If I was shooting wide angle and needed more light I would use 2 strobes aimed straight ahead at a high setting. If this didn't give me enough light I would increase ISO 1 stop. And if I was still short on light, I would decrease the F stop by one stop.

But you know all of this so maybe there is some other problem.

For those new to exposure, see the following "tutorial"

http://www.splashdowndivers.com/photo_gall...gs_exposure.htm

Hi Peter,

A very good link with lots of information.

I did not realise that the shutter speed had no major effect when using flash, other than darkening the background when using a high speed. But, when you think about it the strobe intensity on full is extremerly bright..Iain